import java.util.Scanner;

public class TEST {
    public static void main(String[] args) {

    }
    public static void main2(String[] args) {

            //出现数字9的数字
            public static void main1(String[] args) {
                int count=0;
                for(int i=1;i<=100;i++){
                    if(i%10==9){
                        System.out.println("出现数字9的数字有"+i);
                        count++;
                    }

                }
                System.out.println("一共有"+count+"个数");
            }

            //判断素数
            public static void main4(String[] args) {

                while(true){
                    Scanner scanner=new Scanner(System.in);
                    System.out.print("请输入一个数字：");
                    int num=scanner.nextInt();
                    int i=2;
                    for (i = 2; i <=num ; i++) {
                        if(num%i==0){
                            break;
                        }
                    }
                    if(i==num)
                        System.out.println(num+"是素数");
                    else
                        System.out.println(num+"不是素数");
                    i=2;
                }

            }

            //判断素数
            public static void main5(String[] args) { //最大公约数
                Scanner scanner = new Scanner(System.in);
                while (true) {
                    System.out.print("请输入第一个数：");
                    int num1 = scanner.nextInt();
                    System.out.print("请输入第二个数：");
                    int num2 = scanner.nextInt();
                    int tmp = (num1 > num2) ? num2 : num1;
                    for (int i = tmp; i >= 1; i--) {
                        if (num1 % i == 0 && num2 % i == 0) {
                            System.out.println("最大公约数是" + i);
                            break;
                        }
                    }
                }
            }

            //计算1/1-1/2+1/3-1/4+1/5 …… + 1/99 - 1/100 的值
            public static void main6(String[] args) {
                double i=1.0;
                double sum=0;
                int k=1;
                for(int f=1;f<=100;f++)
                {
                    sum=1/i*k+sum;
                    i++;
                    k*=-1;
                }
                System.out.println(sum);
            }

            //打印x图形
            public static void main7(String[] args) {
                while(true) {
                    System.out.print("请输入行数：");
                    int k=1;
                    Scanner scanner = new Scanner(System.in);
                    int r=scanner.nextInt();
                    for(int i=1;i<=r;i++) {
                        for(int l=1;l<=r;l++)
                        {
                            if(i==l||l==r-i+1) {
                                System.out.print("*");
                            }
                            else {
                                System.out.print(" ");
                            }

                        }
                        System.out.print("\n");
                    }

                }
            }

            //模拟登陆
            public static void main8(String[] args) {
                int flag = 1;
                String str = "123456";
                while (flag <= 3) {
                    System.out.print("请输入您的密码：");
                    Scanner scanner = new Scanner(System.in);
                    String input = scanner.nextLine();
                    if (input.equals(str)) {
                        System.out.println("登陆成功");
                        break;
                    }
                    else {
                        System.out.println("密码错误，登陆失败，请重新输入");
                        flag++;
                    }
                }
                if(flag>3)
                {
                    System.out.println("退出登录，请联系相关工作人员修改密码");
                }
            }


            //输出9*9乘法表
            public static void main9(String[] args) {
                for (int l = 1; l <=9 ; l++) {
                    for (int r = 1; r <=l; r++) {
                        System.out.print(r+"*"+l+"="+(l*r)+" ");
                    }
                    System.out.println("\n");
                }

            }

        }
    }

